As awareness of the detrimental effect of fluorocarbons on the environment increases and government regulations on the release of fluorocarbons become more stringent, the use of refrigerant recovery systems is becoming more widespread. Refrigerant recovery systems are designed to draw refrigerant from disabled refrigeration systems. Typical refrigeration systems include household refrigerators, air conditioning units, heat pumps, vending machines for soft drinks, water coolers for drinking water, and other small air conditioning and refrigerating systems. Such systems typically use chlorofluorocarbons (CFC's), hydrochlorofluorocarbons (HCFC's) or other heat transfer medium. The use of CFC's as refrigerants is discussed in detail in U.S. Pat. No. 5,020,331, which is hereby incorporated by reference in its entirety.
When the compressor of such a refrigeration system is burned out, the motor winding of the compressor is melted and releases resins and acids into the refrigerant which are harmful to the refrigeration system. The contaminated refrigerant may be removed and recovered by use of a refrigerant recovery system and subsequently cleaned and recycled.
Many refrigerant recovery systems include a compressor for removing substantially vaporized refrigerant from a disabled refrigeration system and expelling the refrigerant from the compressor at an outlet pressure higher than the inlet pressure. Some of the contaminants contained within the refrigerant may be absorbed by the oil in the compressor of the recovery system. Therefore, it is often desirable if not necessary to change the oil in the compressor of the recovery system between different recovery operations. Contaminated compressor oil is typically drained through an oil outlet port and clean oil recharged through an oil inlet port. A small amount of compressor oil may dissipate during operation. In the event that the level of oil in the compressor is insufficient, additional oil may be added to the compressor through the oil inlet port. If the compressor is operated with insufficient lubricating oil for a sufficient period of time, it too will "burn out."
Various means are typically used to determine and/or monitor the level of lubricating oil in the compressor. For example, a sight glass has been mounted at the distal end of an elongated, L-shaped tube which was fluidly connected to the compressor housing However, compressor failure has occurred with the such indicators due to lack of lubrication even though the sight glass at the end of the L-shaped tube indicated that lubricant was present in the compressor because the L-shaped tube was not oriented properly with respect to the compressor housing. In particular, because of its extreme length, the distal end of the tube was often downwardly pitched. Even at a relatively small angle lubricant would collect at the distal end of the L-shaped tube and give an erroneous indication of an adequate level of lubricant in the compressor.
Many compressors are also provided with a separate drain outlet and plug in the bottom of the compressor housing for draining lubricant from the compressor. However, users typically encounter difficulties in completely draining lubricant from the compressor housing. When the unit is recharged, new refrigerant cycled through the compressor may then become contaminated. It would be advantageous to have a single device which may be coupled to a compressor or other container which provides a reliable indication of the oil level in the compressor and permits essentially complete draining of the compressor to inhibit cross-contamination between oil charges.